The subject of the present invention is a valve for a scroll compressor, and more particularly a valve placed between the compression stage of the compressor and the high-pressure compartment thereof.
The valve according to the invention is equally applicable to scroll compressors comprising a fixed spiral element and a movable spiral element as to compressors in which both spiral elements can be moved.
FIG. 1 of the appended schematic drawing shows a scroll compressor in which one of the spiral elements is fixed and the other can be moved.
Such a scroll compressor comprises an enclosure 2, the upper part of which is formed by a cap 3. This enclosure 2 is separated into two compartments, a low-pressure gas-inlet compartment 4, and a high-pressure compartment 5 for outlet of the compressed gas. Theses two compartments are separated by a gas compression stage 6. The gas is admitted into the low-pressure compartment via an inlet orifice 7 and the compressed gas is discharged from the high-pressure compartment 5 via an orifice 8.
The compression stage 6 consists of a fixed spiral element 9 and a movable spiral element 10, these two elements comprising interpenetrating parts and together defining compression pockets 12. The movable spiral element 10 is driven by a shaft 13, in an orbital movement, the movement of the shaft 13 being provided by a motor 14. During the orbital movement of the element 10, the compression pockets 12 have a volume which gradually decreases from the outside, where the gas is admitted into the low-pressure compartment, towards the inside, the compressed gas leaving at the centre of the compression stage 6 to the high-pressure compartment 5 through a valve denoted by the general reference 15 in FIG. 1.
This valve is a delivery valve which prevents the return flow of fluid from the high-pressure chamber 5 to the compression pockets 12. This valve plays a role, not only in shut-down of the compressor, but also in operation, in so far as when the compression stage has a fixed compression rate and when the last compression pocket is in communication with the outlet orifice of the gas, the pressure may be less than the pressure in the high-pressure chamber 5. The valve therefore isolates the chamber 5 from the compression pockets while the pressure upstream of the valve is less than the pressure in the high-pressure chamber.
There are various solutions for producing delivery valves. Some valves consist of one or more lamella plates which are free or combined with springs.
Other valves, such as those described in document U.S. Pat. No. 6 179 589, or in document JP 07 127 745 comprise a convex shape, having an active surface which is rounded or of frustoconical shape.
The various valves known on the market have a number of drawbacks and especially produce a considerable dead volume upstream of the valve, allowing the gas to expand in the following pocket, giving high pressure drops, causing turbulent flow resulting in a high acoustic level of operation, some of them being of large mass resulting in a long response time and providing a path for the gas which has edges, which disturbs the fluid flow.
The aim of the invention is to provide a valve for a scroll compressor, reducing the pressure drops and the turbulence on passage of the gas, and delimiting, upstream of the valve, as small a dead volume as possible.
To this end, the valve to which it relates, designed to be fastened to the element of the compression stage located on the same side as the high-pressure compartment, comprises a central profiled body designed to protrude in an opening for outlet of the gas from the compression stage, the outer axisymmetric surface of which is concave, of generally toroidal shape, and is terminated by a tip, the outlet opening of the compression stage being delimited by a curved surface forming, in the downstream direction, a widening providing, with the central profiled body, a cross section for the passage of the gas which is substantially constant, closing means being provided in order to seal this passage in the closed position of the valve.
Given the shape of the central part of the valve, and especially of the pointed end thereof, there is no blocking of the gas at this end. Furthermore, the toroidal shape of the outer surface of the valve provides a gradual change of direction, without any discontinuity, since there are no edges, and the cross section and the gas speed are kept substantially constant. The valve therefore has very quiet operation, and the pressure drops are small. Furthermore, the protrusion of the central profiled body into the opening for outlet of gas from the compression stage limits the dead volume.
According to a first embodiment of this valve, at least part of the central profiled body can be moved axially, forming a closing element.
According to one possibility in this event, the entire central body is mounted so that it can slide on a fixed central support and is subjected to the action of a spring placed between the support and the body promoting the actuation of the body to pass to its closed position, when the pressure in the high-pressure compartment is greater than the pressure of the gas at the outlet of the compression stage.
According to another possibility in this event, the central profiled body is made in two concentric parts: a central part belonging to a fixed support and comprising the tip, and a peripheral part mounted so that it can slide on the central fixed part, this second part forming the closing element and closing the valve under the action of a spring by pressing on the curved surface delimiting the outlet opening of the compression stage, when the pressure in the high-pressure compartment is greater than the pressure at the outlet of the compression stage, the outer surfaces respectively of the central part and of the peripheral part being in alignment with each other and delimiting the toroidal surface, in the open position of the valve.
It should be noted that, given the shapes of the outer surface of the central body and of the curved surface which delimits the opening for outlet of the gas, respectively, contact of the central body on the curved surface which forms a seat is made along an edge, so that there is no risk of the valve sticking on its seat in the closed position, when the gas is charged with oil.
According to another embodiment of this valve, the central profiled body is fixed and a specific valve element is designed for closing the valve.
According to one possibility in this second case, the outlet opening of the compression stage ends in the bottom of a recess of generally cylindrical shape, the central profiled body being fastened to a support body held at some distance from the bottom of the recess, this support body being equipped with a closing plate subjected to the action of a spring, for facilitating the closure action, and designed, in the closed position of the valve, to bear against the bottom of the cylindrical recess, in order to seal the annular space between the central profiled body and the surface delimiting the outlet opening of the compression stage.
Advantageously, the support body comprises axial holes ending on the same side as the high-pressure compartment in order to subject the surface of the closing plate and/or of the spring acting on this plate to the pressure of the high-pressure compartment.
In any event, the invention will be clearly understood by means of the following description, with reference to the appended schematic drawing, presenting several embodiments of this delivery valve by way of non-limiting examples.